The present invention relates to light sources and more particularly to a high throughput illuminator useful in the photomicrographic processes employed in integrated circuit manufacture.
In the manufacture of integrated circuits, it is typically necessary to generate photographically very fine patterns, either directly on the semiconductor materials or on masks employed as intermediate images. To generate very high resolution images without incurring very long exposure times, it becomes necessary to employ a light source or illuminator which is very bright and approximates a point source to some extent. Field uniformity and minimum extraneous heat generation are also important attributes.
While the ultimate light source in nearly every case is a lamp of some sort, typically a high pressure mercury arc lamp, there is diminishing utility in going to ever more powerful lamps. Along with high light output, more powerful lamps involve larger arc or filament dimensions. Thus, no matter what optical techniques are employed, the output aperture of the illuminator must be correspondingly larger or it will mask a significant position of the available light energy. Accordingly, there is a considerable premium on increasing efficiency and throughput without merely increasing lamp power.
Among the several objects of the present invention may therefore be noted the provision of a high throughput illuminator useful for photomicrographic processes; the provision of such an illuminator which approximates a point source; the provision of such an illuminator which gathers a relatively high percentage of the light available from a given lamp and efficiently directs that light through an exit aperture approximating a point source; the provision of such an illuminator which is reliable and is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.